javaNIO的第一个例子

功能描述：一个服务器端，多个客户端，客户端向服务器端发送消息，服务器端转发给所有客户端（包括发送者）。

 

服务器端代码：

package com.imooc.nio;


import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.UUID;

public class NioServer {
    public static void main(String[] args) throws Exception {
        /**
         * 开启一个服务端
         * 设置为非阻塞
         * 绑定端口号
         */
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.configureBlocking(false);
        serverSocketChannel.bind(new InetSocketAddress(8080));

        Selector selector = Selector.open();
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        //UUID->客户端连接
        Map clientMap = new HashMap<>();

        while (true) {
            selector.select();

            Set selectionKeys = selector.selectedKeys();
            selectionKeys.forEach(selectionKey -> {

                try {
                    if (selectionKey.isAcceptable()) {
                        /**
                         * 服务端接收到连接
                         * 保存接收到的客户端连接
                         */
                        ServerSocketChannel server = (ServerSocketChannel) selectionKey.channel();
                        SocketChannel socketChannel = server.accept();
                        socketChannel.configureBlocking(false);
                        socketChannel.register(selector,SelectionKey.OP_READ);
                        String key = UUID.randomUUID().toString();
                        clientMap.put(key,socketChannel);
                        System.out.println(socketChannel.getRemoteAddress()+"连接上了服务器");
                    } else if (selectionKey.isReadable()) {
                        /**
                         * 读取客户端消息
                         * 转发到所有客户端
                         */
                        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
                        try {
                            ByteBuffer buffer = ByteBuffer.allocate(1024);
                            int len = socketChannel.read(buffer);

                            if (len > 0) {
                                buffer.flip();
                                Charset charset = Charset.forName("UTF-8");
                                String receiveMsg = String.valueOf(charset.decode(buffer).array());
                                String key = null;
                                for (Map.Entry entry : clientMap.entrySet()) {
                                    if (entry.getValue() == socketChannel) {
                                        key = entry.getKey();
                                        break;
                                    }
                                }
                                String sendMsg = key + ":" + receiveMsg;
                                System.out.println(sendMsg);
                                for (Map.Entry entry : clientMap.entrySet()) {
                                    ByteBuffer writeBuffer = ByteBuffer.allocate(1024);
                                    writeBuffer.put(sendMsg.getBytes());
                                    writeBuffer.flip();
                                    entry.getValue().write(writeBuffer);
                                }
                            }
                        }catch (Exception e) {
                            e.printStackTrace();//java.io.IOException: 远程主机强迫关闭了一个现有的连接。
                            socketChannel.close();
                        }
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
            selectionKeys.clear();
        }

    }
}

客户端代码：

package com.imooc.nio;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class NioClient {
    public static void main(String[] args) throws Exception {
        /**
         * 开启一个客户端
         * 设置为非阻塞
         * 连接到服务器
         */
        SocketChannel socketChannel = SocketChannel.open();
        socketChannel.configureBlocking(false);
        socketChannel.connect(new InetSocketAddress("localhost",8080));

        Selector selector = Selector.open();
        socketChannel.register(selector, SelectionKey.OP_CONNECT);

        while (true) {
            selector.select();

            Set selectionKeys = selector.selectedKeys();
            for (SelectionKey selectionKey : selectionKeys) {
                if (selectionKey.isConnectable()) {
                    /**
                     * 客户端已连接
                     * 开启一个线程监听控制台输入
                     */
                    SocketChannel client = (SocketChannel) selectionKey.channel();
                    if (client.isConnectionPending()) {
                        client.finishConnect();
                    }
                    client.register(selector,SelectionKey.OP_READ);
                    ExecutorService executor = Executors.newSingleThreadExecutor();
                    System.out.println(socketChannel.getLocalAddress()+"连上了服务器");
                    ByteBuffer writeBuffer = ByteBuffer.allocate(1024);
                    executor.submit(()->{
                        try {
                            while (true) {
                                writeBuffer.clear();
                                BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
                                String line = reader.readLine();
                                writeBuffer.put(line.getBytes());
                                writeBuffer.flip();
                                client.write(writeBuffer);
                            }
                        }catch (Exception e) {
                            e.printStackTrace();
                        }
                    });
                } else if (selectionKey.isReadable()) {
                    /**
                     * 打印服务端消息
                     */
                    SocketChannel client = (SocketChannel) selectionKey.channel();
                    ByteBuffer readBuffer = ByteBuffer.allocate(1024);
                    int len = client.read(readBuffer);
                    System.out.println(new String(readBuffer.array(),0,len));
                }
            }
            selectionKeys.clear();
        }
    }
}